Day: December 21, 2002

其實他根本就是一個 wrapper
把 .net 的 code 給包裝起來
看起來的確變的很類似 vfp
但實際上宣告變數以及語法仍然遵循 c# 或 vb.net
而非原來的 vfp
不過文件上說的沒錯
他提供了絕大部分的 vfp 函數
可是~
存取資料時
仍然要使用 sqlconnect
而不是 use
也因此沒有索引的功能
但有提供索引搜尋跟切換索引的功能
只是這些東西仍然依存於 .net dataview 元件的能力
換言之
如果要細調其執行效能
恐怕仍然需要了解 .net ado.net
source code 很有幫助,並不是很困難
建議也下載回去看
對上手 .net 有相當的助益

限制:
以6.0而言,似乎一定要用 ado 來開啟
範例:
OConn = CREATEOBJECT(“ADODB.Connection”)
OConn.ConnectionString = “provider=vfpoledb.1;;
data source=.\testdbc.dbc”
OConn.Open
語法:
Provider = VFPOLEDB
Data Source=cPath
Specifies the path to the Visual FoxPro database or folder containing free tables. For example, d:\vfp7\samples\data\testdata.dbc
Mode=cMode
Specifies one of the following: Read, ReadWrite, Share Deny None (default), Share Deny Read, Share Deny Write, Share Exclusive (inclusive of the previous two modes).
可以丟如下指令
The Visual FoxPro OLE DB Provider supports the native Visual FoxPro language syntax for the following commands:
CREATE TABLE – SQL Command
Creates a table having the specified fields.
DELETE – SQL Command
Marks records for deletion.
DROP TABLE Command
Removes a table from the database specified with the data source and deletes it from disk.
INSERT – SQL Command
Appends a record to the end of a table that contains the specified field values.
SELECT – SQL Command
Retrieves data from one or more tables.
UPDATE – SQL Command
Updates records in a table with new values.
The Visual FoxPro Language Reference contains detailed information about the following supported commands:
ALTER TABLE – SQL Command
Programmatically modifies the structure of a table.
CREATE TABLE – SQL Command
Creates a table having the specified fields.
Using Data Definition Language (DDL)
You cannot include DDL in the following places:
In a batch SQL statement that requires a transaction
Following a previously executed statement that required a transaction if not in auto-commit mode and if your application has not yet called SQLTransact.
For example, if you want to create a temporary table, you should create the table before you begin the statement requiring a transaction. If you include the CREATE TABLE statement in a batch SQL statement that requires a transaction, the provider returns an error message.
DELETE – SQL Command
Marks records for deletion.
DELETE TAG Command
Removes a tag or tags from a compound index (.cdx) file.
DROP TABLE Command
Removes a table from the database specified with the data source and deletes it from disk.
INDEX Command
Creates an index file to display and access table records in a logical order.
INSERT – SQL Command
Appends a record to the end of a table that contains the specified field values.
SELECT – SQL Command
Retrieves data from one or more tables.
The Visual FoxPro OLE DB Provider supports the native Visual FoxPro language syntax for this command.
SET ANSI Command
Determines how comparisons between strings of different lengths are made with the = operator in Visual FoxPro SQL commands.
SET BLOCKSIZE Command
Specifies how disk space is allocated for the storage of memo fields.
SET COLLATE Command
Specifies a collation sequence for character fields in subsequent indexing and sorting operations.
SET DELETED Command
Specifies whether records marked for deletion are processed and whether they are available for use in other commands.
SET EXACT Command
Specifies the rules for comparing two strings of different lengths.
SET EXCLUSIVE Command
Specifies whether table files are opened for exclusive or shared use on a network.
SET NULL Command
Determines how null values are supported by the ALTER TABLE – SQL, CREATE TABLE – SQL, and INSERT – SQL commands.
SET PATH Command
Specifies a path for file searches.
Provider Remarks
If you issue SET PATH in a stored procedure, it will be ignored by the following functions and commands: SELECT, INSERT, UPDATE, DELETE, and CREATE TABLE
If you issue SET PATH in a stored procedure and do not subsequently set the path back to its original state, other connections to the database will use the new path (because SET PATH is not scoped to data sessions).
If you want to create, select, or update tables in a directory other than that specified by the data source, specify the full path of the file with your command.
SET REPROCESS Command
Specifies how many times or for how long to lock a file or record after an unsuccessful locking attempt.
SET UNIQUE Command
Specifies whether records with duplicate index key values are maintained in an index file.
UPDATE – SQL Command
Updates records in a table with new values.